As is well known, and the subject of ordinary biology text books, the skin is a complex system with protective epidermal layers, growing endodermal layers, often a keratinous outer layer, systems of glands and follicles and systems for the supply of intracellular and extracellular fluids. Active methods and compositions for treating the skin which do more than provide a passive coating on it, must take account of its complexity.
Many cosmetic formulations are known for skin treatment that show beneficial effects in improving skin appearance and which work by promoting skin renewal. Renewal is stimulated as a natural process by removal of the outer keratinous layer of the skin system. Such removal can be effected mechanically, for example by abrasive means, or chemically by agents promoting skin system imbalances or destruction of one or more layers of the skin system. Such substances are often described as exfoliants.
EP 0 336 812 published Nov. 10, 1989, discloses the use of a combination of a pyrimidine derivative with a salicylic acid derivative to stimulate hair growth and reduce hair loss. A preferred pyrimidine is minoxidil. The examples disclose n-octanoyl-5 salicylic acid or n-decanoyl-5 salicylic acid used in combination with minoxidil. Minoxidil is an expensive prescription product. As is acknowledged in EP 0 336 812, page 2, line 26 salicylic acids are known to have keratolytic activity, but they are also irritants. The preferred salicylic acids disclosed in the Examples have carbonyl moieties in the 5 position through which a substantial alkyl group is coupled. Similar salicylic acids with a chain of at least three carbon atoms coupled at the five position through a carbonyl group are disclosed in EP 0 378 936 for the treatment of aging of the skin.
EP 0423 929 discloses the use of a class of lactic acid compounds including lactic acid and salts thereof as skin-whitening agents.
EP 0 273 202 published Jun. 7, 1988 contains a broad spectrum disclosure of the use of wide ranges of hydroxy acids as additives to enhance the topical actions of cosmetic and therapeutic agents by enhancing skin penetration and efficacy. Several classes of hydroxy acids are disclosed in EP 0 273 202 A2 for use as additives, namely hydroxymonocarboxylic acids, hydroxydicarboxylic acids and an extensive third class which is a miscellaneous recitation of hydroxycarboxylic acids including acids with cyclic moieties. This class is exemplified by a list of some twenty or thirty compounds. Free acid, lactone and salt forms of the acid are included. 2-hydroxypropanoic acid, lactic acid, is recited, as one acid amongst many, in three and one half pages of disclosure relating to the acid additive to be used in the invention. Examples 3, 6, 8, 15, 19 and 26 of 29 Examples employ lactic acid to enhance the penetration and efficacy of minoxidil, thionicotinamide, clotrimazole, dipyridamole, octyl dimethyl PABA with dioxybenzone and hydroquinone.
At p.2, lines 35 et seq. EPA provides a very general listing of categories of cosmetic and pharmaceutical agents that is enhanced by these additives. These categories are given by way of examples of any natural or synthetic substances intended for topical application to the skin of humans or animals. Such natural and synthetic substances make up the wide field of application of the invention of this prior publication. Substances whose activity is purportedly enhanced by the invention of the EPA include anesthetics, softeners, foot care agents vitamins, tanning agents and the like. Clearly any topically useful substance is intended to be included. Claim 3 of the publication recites salicylic acid among some fifty or sixty or more specific cosmetic or pharmaceutical agents that are subjects of the application, but there appear to be no examples or test data to show what effect, if any, one of the three classes of hydroxy acid of the EPA invention has on the activity of salicylic acid.
Some comparative test data, page 16, apparently show enhancement of the activity of thio- and 6-aminonicotinamides by lactic acid, but there is no differentiation between the effects of various hydroxy acids.
In its preferred embodiments, the present invention provides what are colloquially known as anti-aging formulations and hair-loss remedies having advantages aver the prior art formulations available heretofore.
It is one object of the invention to provide a skin-conditioning composition which can improve the appearance of skin without inducing excessive irritation.
Another object of the invention is to provide a skin-conditioning composition which will promote, stimulate or accelerate skin renewal, again with tolerable or reduced irritation levels.
It is a further object of the invention to provide such a formulation which is a non-prescription product suitable for direct over-the-counter sales to consumers.
A still further object is to provide such a skin-conditioning composition in a dermatological formulation suitable for professional use.
Yet another object of the invention is to provide a skin-conditioning composition for use on the scalp that can improve hair condition and is suitable for direct over-the-counter sales to consumers, for use without professional supervision.